From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benno Senoner Date: Wed, 27 Oct 1999 20:39:18 +0000 Subject: Re: HZ > 100 overhead Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sound@vger.kernel.org On Wed, 27 Oct 1999, Paul Barton-Davis wrote: > >> >Wouldn't you say that an HZ > 100 kernel is the cleanest solution? > >> > >> its the cleanest, but not the best. HZ = 1000 adds about 8% overhead > >> to IRQ processing *all the time*. > > > >Are you *sure* about this? I seem to remember there was some debate > >about that figure on linux-kernel. > > Ed Hall measured it, and my overall impression of Ed is that I'd trust > him to do this correctly. what did the l-k folks think ? It depends on your box, a P133 might suffer much more than a PII400. On a PII400 the performance his is very little IMHO (no actual numbers) But we can't assume that HZ00 for our multimedia apps. Therefore my proposal is the following: (similar to Eric's proposed rtcd) In our upcoming multimedia API we will run the audio daemon not only for providing PCM/MIDI services but precise timers too. This could be implemented by choosing the most efficient method at the moment: that means: if you are runnnig with 1ms audio buffer sizes, instead of firing up the RTC device, use the soundcard's timer (combined with RDTSC) , to wakeup your clients. comments ? Benno.